Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$33.81	5.398%	$35.6351	$35.64	$35.65	$35.60
Purchase #2	$153.89	3.178%	$158.7806	$158.78	$158.80	$158.80
Purchase #3	$179.99	5.596%	$190.0622	$190.06	$190.05	$190.10
Purchase #4	$123.71	10.354%	$136.5189	$136.52	$136.50	$136.50
Purchase #5	$137.97	8.320%	$149.4491	$149.45	$149.45	$149.40
Purchase #6	$168.89	9.566%	$185.046	$185.05	$185.05	$185.00
Purchase #7	$84.50	7.781%	$91.0749	$91.07	$91.05	$91.10
7 purchase totals =	$882.76		$946.5668	$946.57	$946.55	$946.50